Abstract
The purpose of this study is to demonstrate combustion fluctuation phenomena concerning relationship between pressure variation in the cylinder or in the exhaust pipe and the hydrocarbon (HC) emission variation of a light-loaded small two-stroke engine. High level and large variation of total-HC emissions were measured in time-series data using a fast-response FID gas analyzer. Scavenging flow comprises fresh mixture gas and burnt gas is discussed with HC emission variation, the pressure variations and the velocity variations at the transfer port and the exhaust pipe which were simultaneously measured. According to the HC emission data, the classes of combustion status are also accurately grouped and the scavenging flow behavior in each combustion cycle is studied on the influence of the pressure variation in the engine.